The effects of Cu content on the microstructure and mechanical properties of FeCoNiAlCu_x high entropy alloys were investigated by X-ray diffraction, scanning electron microscopy with energy disperse spectroscopy, microhardness and compressive tests. The results show that FeCoNiAlCu_x alloys are composed of fcc phase and bcc phase. However, with the increase of Cu content, the fcc phase increases, while the bcc phase decreases. The alloys are typical dendrite microstructure. There are distinct Cu-enrichment...